It's Not Easy to Be a Man After Travelling to the Future (WN) - Chapter 1338: Space Concept.

In the year 241 of the 6th era, Constantinople was in turmoil.Emperor Constantine personally lead his army, which was completely annihilated. The pagan empire, riding on the wave of a great victory, annexed the entire eastern territory of the empire, and its military might pointed directly at the capital.The 17-year-old imperial princess Theodora ascended the throne in crisis, facing what was already a terribly damaged realm.Rome was about to fall.....................The wheels of fate spun wildly as a transmigrator appeared on the streets of Constantinople.“According to the original plot, it was only a matter of time before Constantinople would fall.” he pondered.“Perhaps I should first whisk away the empress.”(The book is categorized under game fantasy worlds, set in a magically altered Middle Ages, and another title is 'I Really Can't Lead This Team')

Kerrigan’s life was never his own. Raised as a pawn in a twisted game, his mind was shattered in a cruel simulation. Now, in the real world, he’s left with only one thing: Veilbreaker—a power to tear through lies, illusions, and hidden truths. But the more he uses it, the more it eats away at his sanity.Haunted by his past, betrayed by those he should trust, Kerrigan must fight not only the monsters that hunt him but the darkness inside himself. Every ally could be an enemy, and every truth could cost him everything. As a deadly war brews on the horizon, Kerrigan is the only one who can stop it—but the price for victory might just be his mind.Can Kerrigan control his power, or will the truth break him first?

An ordinary youth living in the year 2050 in the Western calendar accidentally came to a fantasy world created by the collision of magical elements and supernatural technology at the other end of the dimension…

- Description from novelbuddy

A man betrayed by a comrade dies a wretched death as a third rate swordsman. His existence, his life, his emotions are all a nuisance in the eyes of society. But wait… What’s this green skin? Reincarnated as a goblin? Wait, I went back in time as well?